Why did God begin the Quran with Surat Al-Baqarah, and what is its relationship to Surat Aal-Imran?

The arrangement of the Qur'anic surahs is, most likely, by divine ordinance (tawqifi), and the Qur'an opens with Surat Al-Fatihah. Surahs Al-Baqarah and Al 'Imran share many characteristics. They will precede the Qur'an and its people on the Day of Resurrection, and they are called "Al-Zahrawayn" (the two radiant ones); either because they guide their reader with the lights that emanate from them, or because of the light that results from their recitation on the Day of Resurrection, or because they both encompass what is contained in Allah's Greatest Name (Al-Ism Al-A'zham).